Added basic autoconf configuration for R bindings.

This is only marginally working, and still depends on some manual changes to files such as Redland.i and Redland.R.
Add files to clean during make.
Configure swig to generate NAMESPACE file.
Automatically modify the generated Redland.R file.

Redland.R is generated by SWIG, but it is missing two class definitions.  I manually added these to Redland.R.in and now append that onto Redland.R after SWIG has generated it.  This allows Redland.R to load and tests to pass, but is obviously obscuring a bug in generation which needs to be fixed.